Submitted to: Clinical and Vaccine Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2010
Publication Date: 12/17/2010
Citation: Olsen, S.C., Hennager, S.G. 2010. Immune responses and protection against experimental Brucella suis biovar 1 challenge in non-vaccinated or B. abortus strain RB51-vaccinated cattle. Clinical and Vaccine Immunology. 17(12):1891-1895. Interpretive Summary: Brucella suis is a bacteria that can cause disease in domestic livestock and people. National eradication programs have been ongoing for decades in an effort to eliminate this disease and protect public health. Spillover of disease from feral swine into domestic livestock causes positive diagnostic tests that cannot be differenciated from Brucella abortus infection. This interferes with regulatory efforts to keep Brucella abortus out of cattle and imperils the financial investment made to eliminate the brucellosis from cattle. In this study, cattle were vaccinated with RB51 and protection against experimental challenge with B. suis during pregnancy was evaluated. Although abortions were not noted, vaccinated and nonvaccinated cattle did not differ in protection against B. suis infection or antibody responses. This data will be of benefit to the scientists, livestock producers, and regulatory personnel in understanding the epidemiology and diagnostic responses associated with Brucella suis infection of cattle.
Technical Abstract: Twenty Hereford heifers, approximately 9 months of age, were vaccinated with saline (control) or 2 x 10**10 CFU of Brucella abortus strain RB51 (RB51) vaccine. Immunologic responses after inoculation demonstrated significantly greater (P<0.05) antibody and proliferative responses to RB51 antigens in cattle vaccinated with RB51 as compared to controls. Pregnant cattle received a conjunctival challenge at approximately 6 months gestation with 10**7 CFU of B. suis biovar 1 strains isolated from naturally infected cattle. The fluorescence polarization assay and the buffered acid plate agglutination test had the highest sensitivity in detecting B. suis infected cattle between 2 and 12 weeks after experimental infection. Serologic responses and lymphocyte proliferative responses to B. suis antigens did not differ between control and RB51 vaccinates after experimental infection. No abortions occurred in cattle in either treatment after challenge, although there appeared to be an increased incidence of retained placenta after parturition in both control and RB51 vaccination treatments. Our data suggests that mammary gland is a preferred site for B. suis localization in cattle. Vaccination with RB51 did not reduce B. suis infection rates in maternal or fetal tissues. Our data suggests that although B. suis is unlikely to cause abortions and fetal losses, RB51 vaccination will not protect cattle against infection after exposure.